1. Field of the Invention
The present invention relates generally to ultrasonic horn assemblies, and particularly to such an assembly which may be at least partially immersed in a liquid bath through which cuvettes containing a liquid solution and a reagent tablet are moved in front of the horn so that transmitted acoustic waves cause the tablet to dissolve in the liquid solution in each of the cuvettes.
2. Description of the Known Art
Ultrasonic horn assemblies are known to be used in clinical analyzers, for purposes of dissolving reagent tablets in liquid solutions contained in a number of cuvettes moving along a track path next to the front of the horn assembly. One such clinical analyzer is disclosed in U.S. patent application Ser. No. 575,924, filed Feb. 1, 1984, and assigned to the assignee of the present invention, the contents of which are incorporated in their entirety by reference in the present application.
The known ultrasonic horn assemblies comprise a generally rectangular horn body with a front end face for transmitting acoustic waves, and a rear end face on which a pair of piezoelectric crystal transducers, or converters, are symetrically mounted. The rear end face on the horn body of the known assembly is of a height of about 1.5 inches (3.81 cm), and the front end face on the horn body is of a height of about 0.25 inches (0.64 cm). The difference in height of area between the rear end face and the front end face on the known horn body thus was of a ratio of about six to one, so as to provide a gain factor of 1:6.
Further, the known horn body was made of aluminum and required a polyurethane coating of between 20 to 30 mils (0.51 to 0.76 mm) thickness across the horn body face and other portions of the body. The coating was required to protect the aluminum material of which the horn body was formed from eroding on account of cavitation during operation of the horn assembly. It was found, however, that anti-bacterial agents added to the liquid bath within which the horn assembly was immersed attacked the polyurethane coating on the horn body so as to render the coating ineffective.
Another problem encountered with the known horn assembly was a non-uniformity in the amplitude of acoustic waves transmitted from the front end face of the horn body in the direction along the length of the front end face, so that complete dissolution occured of a reagent tablet in a liquid solution contained in a moving cuvette, was not always assuredly obtained. Further, the above mentioned requirement of horn gain of 1:6 had to be obtained by making the height or area of the rear end face of the horn body six times that of the front end face resulting in a relatively unstable configuration which contributed to unevenness in the generation of acoustic waves from the front end face of the horn body.